A variety of mobility aids have been developed to provide the blind with a means of traveling independently, confidently, and quickly. These aids include sensory devices for sensing potential obstacles. The sensory devices typically transmit a signal in a beam towards an area and then listen to receive a signal reflected off of an object in the area. Because the propagation velocity of the signal is known, the time between the transmit and reflected signals is indicative of the distance of the object from the sensory device.
A primary disadvantage with the prior art is in "sensing" the space between objects, as well as sensing the general outline of the objects themselves. For example, a blind person walking down the street would like to distinguish between people, mail boxes, trees, etc., and of the gaps between them. In essence, the blind person would like to be able to form a mental picture or "footprint" of the surrounding environment. The blind person would also like to be able to form the mental picture from tactile stimulation and/or auditory signals as quickly and accurately as possible. The prior art is devoid of such a sensory device.